Molecules and Genetics : These disciplines, unknown in Darwin's time, only really developed during the last few decades. Until then, evolutionary relationships among organisms were based on anatomy, embryology, development and distribution. Understanding enzymes, proteins, DNA and the genetic code now provides another independent test of evolutionary relationships.

Atoms and Molecules : Two pages that explain the basics of chemistry necessary to under-standing of biological concepts and evolutionary theory. This is a primer, not an intensive course.

Kimball's Biochemistry : Thorough coverage of the basics of biochemistry including many topics such as ATP, Bioluminescence, Cellular respiration, Enzymes, Metabolism, Photosynthesis, The Urea cycle and more.

The Wired Chemist :
Has sections such as an online general chemistry course and 3D models of inorganic and organic molecules, tables of conversions, an NMR bibliography, a database of NMR spectra, and links to job sites and chemistry journals.

Periodic Table : At the Pictorial Periodic Table, check out Stowe's physicist's version (which arranges elements by quantum levels on planes), Benfey's Spiral Periodic Table (where transition and inner transition metals form arms), and even a three- dimensional spinning table. Most tables are clickable and lead to info on each element.

The Periodic Table of Haiku : Visiting writers have provided literary accompaniment for even the most prosaic of elements, from argon to ununoctium. For more element-inspired verse, follow the link to a Periodic Table of Poetry.

Organic Chemistry Help: This serves as a quick refresher if you've forgotten the difference between alkanes and alkenes or can't recall the details of the Friedel-Crafts alkylation. Brisk pages cover the structure, properties, and nomenclature of the major classes of organic molecules and explain common reaction mechanisms.

Chemistry of Odors : A great place to sniff out smell lore is a site created by organic chemist John Leffingwell, who heads a company in Canton, Georgia, that sells databases of odor and flavor chemicals.